Is it plagiarism/OK if I use big parts of someones literature review for the introduction section of my paper?
If you copy the review text from the web into your own thesis it is a clear case of plagiarism.
When you write academic text where there is a need to provide the sources for your information (as references) you need to have read the sources. It is not ok to quote sources without having even looked at them. In very rare cases, may it be acceptable to quote a source quoted by someone else in a publication. These cases may include very hard to find literature or literature in a different language. But, such secondary references should not be used unless deemed absolutely unavoidable.
If you need to cite the on-line review, you will need to look at how web-sources are cited at your school (if they are allowed). you can also look at the recommendations at American Psychological Association (APA; very appropriate for you) and their style site. You may find many other bits and pieces that are of interest to you.
I'm going to disagree with Peter on this.
Almost anything is acceptable if you are utterly utterly open and honest about it. If you lift sections from the review without proper attribution that's plagiarism but if you properly cite and properly quote a block of text from the review with quotation marks and indentation making clear where it is from then it's not plagiarism.
There's nothing wrong with including a quoted block of text with something along the lines of "and this concept is well explained in A. Bsons review [title] (20xx) " followed by a quote (even quite a large quote) which is properly indented and shown to be a quote so that people are clear what are your own words and what has been written by the other author.
Now for one reason or another the review might be incorrect or a poor choice of source or a source that is unacceptable for some other reason within the bounds of what you've been assigned to do or someone may have specifically specified that reviews must not be used as sources but that's all separate from plagiarism.
To answer in the spirit of my answer:
User woj https://academia.stackexchange.com/users/15446/woj on this site once commented that
"I reviewed once a thesis which had a copied/pasted page from a publication (with an authorization from the author and clear citations) and the author added in a footnote that this is by far the best explanation he read and does not see any reason to phrase it differently (that was in an introductory chapter). I was very fine with that."
As a comment in this page: Are you allowed to copy text from your Master's thesis into your PhD thesis?
Here's my two cents. The OP's question is formulated as "is it plagiarism/OK". Therefore, if someone copies large parts of someone's work and provides proper attribution, it is definitely not plagiarism, but it is IMHO strongly not OK. It is not OK for the following two reasons:
most academic guidelines (i.e., dissertation guides) significantly limit the size of direct copy/paste materials, so it is not possible to do that without violating those guidelines;
even in the absence of such guidelines, direct reusing of someone's work represents the (almost complete) lack of academic effort, thus, making that paper/report irrelevant.